A fun stack-based calculator.
Use the browser version here:
https://blackchip-org.github.io/zc
Use tab to auto-complete. First tab completes an operation name as much as possible. Next tab shows matching candidates. When using on a mobile device, use the "tab" button to emulate pressing the tab button twice.
Example use:
https://blackchip-org.github.io/zc/?eval=1+8+seq+[2+sw+pow]+map
When I'm at a terminal prompt and I need to use a calculator, bc has always
been my tool of choice. I thought it would be fun to write a calculator myself
but with some items from my wish list built in. Those items are:
- A stack-based calculator. Typing in a value places it on the stack. An operation consumes values on the stack and places its results back on the stack.
- To minimize the use of the shift key. Instead of using
+for addition, useaddorawhich is easier to type. - Use arbitrary sized integers and fixed point math by default.
1.1 2.2 addshould be3.3and not3.3000000000000003. - Be more than a simple calculator. Need an external tool to lookup, compute, or calculate? Put it in the calculator as a module instead. Make this calculator like a Swiss army knife.
- Auto-complete!
This is the third iteration of this calculator and something fun to work on when time is available. It is a bit rough at this stage but should be useful nonetheless. Also, it will always be a bit rough--full of bugs and inconsistencies. Features get added as I need or think of them. Bugs get fixed or ignored as I see them. There is no grand plan beyond tinkering around for entertainment. Things may change in backwards incompatible ways with no notice.
For the command-line version, install go and then install the calculator with:
go install github.com/blackchip-org/zc/v6/cmd/zc@latest
Run the calculator with:
zc
Each line entered at the calculator prompt is divided into words. Each word is separated by whitespace. A word can be either a:
- value: Starts with a numeric character, a decimal point, a numeric sign, or quotes. Values are placed onto the stack.
- operation: Invokes a operation with the given name. Parameters are consumed from the stack and results are placed on the stack.
If 2 3 a is entered at the prompt, the values of 2 and 3 are placed on
the stack, the a operation (for addition) is executed, the values are
consumed and the result 5 is placed on the stack.
Examples of calculator use will be presented in a table such as:
| Input | Stack |
|---|---|
2 3 a |
5 |
The Input column shows the text entered at the prompt and the Stack column shows the contents of the stack after the line is evaluated. Each word could have been placed on a separate line:
| Input | Stack |
|---|---|
2 |
2 |
3 |
2 | 3 |
a |
5 |
If there are multiple items on the stack, they are notated by using a pipe |
character to separate each item. The item on the right is the top of the stack.
If an operation does not change the stack a notification may be printed right above the prompt. This is indicated in the table by using italics.
| Input | Stack |
|---|---|
0 rand.seed |
seed set to 0 |
The basic math functions are:
| Function | Description |
|---|---|
add, a, + |
Addition |
sub, s, - |
Subtraction |
mul, m, * |
Multiplication |
div, d, / |
Division |
For each of these operations there are three separate names. For addition there is:
a: Easy to type without having to use the shift keyadd: Easy to read in documentation+: Easy to type if you have a keyboard with a number pad
Additional basic math functions can be found in the basic reference.
Let's compute the distance between two points: (2, 3) and (5, 7). The
formula for this uses the Pythagorean theorem:
dist = sqrt((x2 - x1)^2 + (y2 - y1)^2)
The steps are:
- Compute
x2 - x1 - Square the result
- Compute
y2 - y1 - Square the result
- Add them together
- Take the square root
The entry into the calculator looks like the following:
| Input | Stack |
|---|---|
5 2 sub |
3 |
2 pow |
9 |
7 3 sub |
9 | 4 |
2 pow |
9 | 16 |
add |
25 |
sqrt |
5 |
Thousand separators are ignored when parsing numbers:
| Input | Stack |
|---|---|
65,536 sqrt |
256 |
Currency symbols are also ignored when parsing:
| Input | Stack |
|---|---|
$1234 2 mul |
2468 |
Integer math uses arbitrary sized values when possible:
| Input | Stack |
|---|---|
2 128 pow |
340282366920938463463374607431768211456 |
Real number math uses fixed point math when possible:
| Input | Stack |
|---|---|
1.1 2.2 a |
3.3 |
To perform double precision floating-point operation, use add/f instead:
| Input | Stack |
|---|---|
1.1 2.2 add/f |
3.3000000000000003 |
Use either round or r to round to a certain number of digits after the
decimal point:
| Input | Stack |
|---|---|
1.1 2.2 add/f |
3.3000000000000003 |
2 round |
3.3 |
Enter fractions in a/b notation:
| Input | Stack |
|---|---|
1/2 1/4 |
1/2 | 1/4 |
add |
3/4 |
Prefix a whole number to a fraction with either a space, an underscore, or a hyphen:
| Input | Stack |
|---|---|
2-1/2 3-1/4 |
2-1/2 | 3-1/4 |
add |
5 3/4 |
Enter complex numbers in r+i notation:
| Input | Stack |
|---|---|
1+2i 2+3i |
1+2i | 2+3i |
add |
3+5i |
Text can be used as a value by either one of two ways. If the text does not
contain any whitespace, the text can be prefixed with a slash, /. For
example:
| Input | Stack |
|---|---|
1 2 |
1 | 2 |
/add |
1 | 2 | add |
Otherwise, surround text with quotes. Single quotes, ' ', double quotes,
" " or square brackets, [ ] can be used. If the text value is the only item
on the line, an ending quote is not required. The following computes the
length, in characters, of the given text:
| Input | Stack |
|---|---|
'one thousand |
one thousand |
len |
12 |
Using brackets is convenient when nesting quoted values:
| Input | Stack |
|---|---|
1 2 [[[add]]] |
1 | 2 | [[add]] |
eval |
1 | 2 | [add] |
eval |
1 | 2 | add |
eval |
3 |
To use multiple lines as values (for example, when pasting the contents of the
clipboard), use quote with a delimiter that marks the end of the values.
Each line is considered a separate value when using quote. For example:
| Input | Stack |
|---|---|
1 2 add |
3 |
quote EOF |
3 |
2 3 add |
3 | 2 3 add |
EOF |
3 | 2 3 add |
Values on the stack may have annotations to provide some additional metadata. For example, distance calculations and conversions annotate the value with the unit of measure:
| Input | Stack |
|---|---|
1 1 2 2 |
1 | 1 | 2 | 2 |
haversine |
157225.4320380729 m |
m-km 2 round |
157.23 km |
A unit annotation can manually be attached to a value using unit:
| Input | Stack |
|---|---|
123 |
123 |
/m unit |
123 m |
A label can be attached using label:
| Input | Stack |
|---|---|
42 |
42 |
[the answer] label |
the answer: 42 |
Annotations are typically discarded when a value is popped off the stack:
| Input | Stack |
|---|---|
123 /m unit |
123 m |
20 sub |
103 |
Let's say that you commonly have to compute a sales tax that is 5%. To compute the sales tax on something that costs $123:
| Input | Stack |
|---|---|
$123 |
$123 |
dup |
$123 | $123 |
0.05 |
$123 | $123 | 0.05 |
mul |
$123 | 6.15 |
add |
129.15 |
Repeated use of this pattern can be used with a macro:
| Input | Stack |
|---|---|
def tax dup 0.05 mul |
macro 'tax' defined |
$123 |
$123 |
tax add |
129.15 |
The name of = is reserved for your macro use in bulk operations:
| Input | Stack |
|---|---|
def = top f-c 2 round |
macro '=' defined |
32 = |
0 °C |
68 = |
20 °C |
100 = |
37.78 °C |
No operations start with a . character and can be used for macro names. Play
a game of rock, paper, scissors:
| Input | Stack |
|---|---|
1 rand.seed |
seed set to 1 |
def .rps c 'rock' 'paper' 'scissors' rand.take |
macro '.rps' defined |
.rps |
paper |
.rps |
rock |
Macros can also be used to override calculator operations. Undefine the
macro by using def without an expression.
| Input | Stack |
|---|---|
def pi 'Yum |
macro 'pi' overrides |
pi |
Yum |
def pi |
macro 'pi' undefined |
pi 5 r |
Yum | 3.14159 |
The map operation can be used to apply a function to each item on the stack.
To use this operation, the top element of the stack should be an expression
to evaluate. Place this expression on the stack using quotes to prevent
immediate evaluation. For example, to double all numbers on the stack:
| Input | Stack |
|---|---|
1 2 3 4 5 |
1 | 2 | 3 | 4 | 5 |
[2 mul |
1 | 2 | 3 | 4 | 5 | 2 mul |
map |
2 | 4 | 6 | 8 | 10 |
The fold function can be used to reduce all items in the stack to a single
value. For example, to sum all the numbers on the stack:
| Input | Stack |
|---|---|
1 2 3 4 5 |
1 | 2 | 3 | 4 | 5 |
[add |
1 | 2 | 3 | 4 | 5 | add |
fold |
15 |
Additional higher-order functions can be found in the hof reference.
It is sometimes convenient to store values in a temporary stack during
a calcuation. The push operation removes the top item in the main stack
and pushes it to the temproary stack. The pop operation does the inverse.
For example, to compute an average, first get the length of the stack,
push that to the temporary stack, sum the values, pop the length and then
divide:
| Input | Stack |
|---|---|
2 4 4 4 5 5 7 9 |
2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 |
n |
2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 | 8 |
push |
2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 |
sum |
40 |
pop |
40 | 8 |
div |
5 |
The push.all and pop.all operations transfers all items from one stack
to the other. Use the flip operation to flip between the stacks.
Items on the main stack can also be stored to a named memory location to be
recalled at a later time. Use store to copy the stack to memory and load
to recall it.
Let's manually compute the population standard deviation found in the example on
the Wikipedia page. The
average of the all the data points must first be computed and then deviations
from that average are calculated. This time the predefined average operation
is used. The data is first entered into the calculator and then the stack is
saved with the name of data. The average is then computed and stored with the
name of av. The data points are then recalled from memory and the deviations
from the average are calculated for each value. The standard deviation is then
simply the square root of the average deviation.
| Input | Stack |
|---|---|
2 4 4 4 5 5 7 9 |
2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 |
/data st |
stored |
avg |
5 |
/av st |
stored |
c /data ld |
2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 |
[/av ld sub sq] map |
9 | 1 | 1 | 1 | 0 | 0 | 4 | 16 |
avg sqrt |
2 |
The same calculation can be done using the temporary stack like this:
| Input | Stack |
|---|---|
2 4 4 4 5 5 7 9 |
2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 |
copy |
copied |
avg |
5 |
popa |
5 | 2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 |
up |
2 | 4 | 4 | 4 | 5 | 5 | 7 | 9 | 5 |
[sub sq] /map 2 apply |
9 | 1 | 1 | 1 | 0 | 0 | 4 | 16 |
avg sqrt |
2 |
These commands are available when running the calculator interactively:
| Command | Description |
|---|---|
| blank line | Remove the first item from stack |
def |
Define a macro |
redo |
Redo the last undo |
reset |
Clear stacks, memory, and all state |
quit |
Print the final stack and return to shell |
quote |
Add each line to the stack until delimiter is found |
undo, u |
Undo the last line entered |
Any arguments found on the command line are passed to the calculator for a one-time evaluation:
$ zc 2 3 add
5
Using quotes from the command line can be tricky since they are interpreted by the shell:
$ zc 'foo' len
(!) unknown operation: foo
In this case, wrap the expression with quotes and then use square brackets for foo:
$ zc '[foo] len'
3
Use a single argument of - to read from standard input:
$ echo "2 3 add" | zc -
5
Some features of the calculator use external C libraries. The current release binaries do not include these external libraries and using one of these operations will raise a "feature not supported" error.
For coordinate transform support, build with the proj tag and install proj
with:
sudo apt install libproj-dev
- Fixed point math provided by https://github.com/cockroachdb/apd
- CLI auto completion and history provided by https://github.com/peterh/liner
- Geospatial transformations provided by https://github.com/twpayne/go-proj
- Emoji JSON file provided by https://github.com/muan/unicode-emoji-json
- Terminal demo created with https://github.com/faressoft/terminalizer
Contact me at [email protected]