beads-lang is a programming language created in 2016 by Edward de Jong.
| #1826on PLDB | 8Years Old |
beads level 1 program calculator
// flutter version available at: on github, look for: flutter-calculator-demo
// article: https://itnext.io/building-a-calculator-app-in-flutter-824254704fe6
const
C_OP = #3E424D // keycap fill for an operator like C
C_DIGIT = #6E6E6E // keycap fill for a digit
C_ARITH = #1A4C6E // keycap fill for arithmetic buttons
// warning: you must use the same unicode math chars in case statements later in arithmetic()
KEYCAPS = [ 'C', '±', '%', '÷', // tried \u207A\u2215\u208B instead of ± but it is ugly
'1', '2', '3', 'x',
'4', '5', '6', '−', // \u2212 is the minus sign
'7', '8', '9', '+',
'', '0', '.', '='] // '⌫' is U+232B, for future undo key
KEYCOLORS = [C_OP, C_OP, C_OP, C_ARITH,
C_DIGIT, C_DIGIT, C_DIGIT, C_ARITH,
C_DIGIT, C_DIGIT, C_DIGIT, C_ARITH,
C_DIGIT, C_DIGIT, C_DIGIT, C_ARITH,
C_OP, C_DIGIT, C_OP, C_ARITH]
SPACING = 3 // points between each cell
HAIR = "\u2009" // a thin space 200A is even thinner
record a_term
ss : str // the string containing the contents of the term
op : str // the operator in keycap string form '+', '-'...
record a_state
terms : array of a_term
termx : num // which term we are on
chain_op : str // chain operator char for repeated = presses
chain_val: num // chain value to repeat
fresh : yesno // if this is Y, then next digit will clear existing value
var g : a_state
calc main_init
g.terms[1].ss = ""
g.termx = 1
g.fresh = Y
vert slice main_draw
var cellsize = if b.box.width > b.box.height then b.box.height/8 else b.box.width/4
var result_v = cellsize*2 // need to enhance compiler so that expressions don't get converted
var keys_v = cellsize*5
var keys_maxh = min(b.box.width, cellsize*8) // don't go wider than 8 squares wide (double)
draw_rect(b.box, fill:#121F30)
skip 10 al
add result_v px d_result
add keys_v px d_keys(keys_maxh)
skip 10 al
draw d_result
draw_rect(b.box, fill:#0D161F)
// build the string out of the active terms
var s : str = ""
loop array:g.terms index:i
g.terms[i].ss &=> s
if g.terms[i].op <> U
HAIR & g.terms[i].op & HAIR &=> s // append the operator
if (s == "")
s = "0" // when nothing is entered into our expression, call it zero
draw_str(b.box, s, size:b.box.height*0.5, just:RIGHT, indent:20 pt, color:WHITE)
horz slice d_keys(
totwidth -- max width we allow for the grid, might be all of the space
)
// in landscape mode, we don't want the key grid to get too wide, looks bad
skip 10 al
add totwidth px d_keygrid
skip 10 al
table d_keygrid
horz slice
skip SPACING pt
loop reps:4
add 10 al
skip SPACING pt
vert slice
skip SPACING pt
loop reps:5
add 10 al
skip SPACING pt
// inside grid cell draw function, b has properties b.box, cell_seq, cell:a_xy, nrows, ncols
cell
draw_rect(b.box, fill:KEYCOLORS[b.cell_seq], corner:6 pt)
draw_str(b.box, KEYCAPS[b.cell_seq], size:b.box.height, color:WHITE)
track EV_TAP
// respond to the command
case b.cell_seq
| 1 // clear
do_clear
| 2 // plusminus - change the sign of the current term
sign_change(g.termx)
| 3 // percent - divide the current term by 100
do_percent
| 4, 8, 12, 16 // arithmetic operations
do_arith(KEYCAPS[b.cell_seq])
| 17 // future feature - backspace
nop // do_backspace
| 19 // period
do_period
| 20 // equals
do_equals
else
// must be a digit
add_digit(KEYCAPS[b.cell_seq])
// calc do_backspace
// log "backspace"
// reserved for future undo functionality
// this will test ability to read code and extend it
calc do_percent
// if the current term is empty do nothing
// apple's calculator takes the sequence 900+% and makes it 900^2 which is nutty
if g.terms[g.termx].ss <> ""
if g.termx > 1
// when we have two terms, like 300 + 20% we take 20% of the first term and replace
g.terms[g.termx].ss = to_str(eval(g.termx)*eval(g.termx-1)/100)
else
// we only have 1 term, so just divide it by 100
g.terms[g.termx].ss = to_str(eval(g.termx)/100)
g.fresh = Y
calc eval (
termx -- term index to evaluate
) : num // convert a term to a floating point number
var ss : str = g.terms[termx].ss
if ss == ""
return 0
return to_num(ss)
calc do_clear // clear the current term to blank.
// if the user has entered 123+, there is an empty current term will do nothing
g.terms[g.termx].ss = ""
calc sign_change(
tx -- term index
)
var old : str = g.terms[tx].ss
if old == ""
// we have no operand yet in the current term, so
// either ignore it or change previous operand's sign
// this is what apple's calculator does
if tx > 1
sign_change(tx-1) // change previous operand's sign. kinda weird really.
elif str_begins(old, "-")
g.terms[tx].ss = str_subset(old, from:2) // strip the minus
else
g.terms[tx].ss = '-' & old // prepend a minus
calc do_period
// ignore attempts to add more than one period
var list : array of num
str_find(g.terms[g.termx].ss, ".", list)
if tree_count(list) == 0
add_digit(".") // no period yet, so append one
calc do_equals
var val = eval(1) // start with the first term by itself
var val2
// if there is no second or later term use the chain operator and value
if tree_count(g.terms) < 2
// use repeat if we have one
if g.chain_op <> U
val = arithmetic(g.chain_op, val, g.chain_val)
else
// two or more terms to process
loop from:1 index:tx while:g.terms[tx+1].ss <> "" and g.terms[tx].op <> U
val2 = eval(tx+1)
// remember the last operator we used as our chaining value
g.chain_op = g.terms[tx].op
g.chain_val = val2
val = arithmetic(g.chain_op, val, val2)
// calculation done, convert the value back as if we entered it
trunc g.terms // zap the array
g.terms[1].ss = to_str(val) // replace our value
g.termx = 1
g.fresh = Y
calc arithmetic(
operand : str -- operation like "+", must match keycap
term1 : num
term2 : num
) : num -- resulting value
var result
case operand // note: these operators must match the keycaps
| '+'
term1 + term2 => result
| '−'
term1 - term2 => result
| 'x'
term1 * term2 => result
| '÷'
term1 / term2 => result
else
result = ERR
return result
calc add_digit(
digit : str // digit to append to current term
)
// if we are starting fresh, then erase what was there before
// we also replace the previous string if it was a leading zero
if g.fresh or g.terms[g.termx].ss == "0"
g.terms[g.termx].ss = "" // clear whatever was there
digit &=> g.terms[g.termx].ss
g.fresh = N
calc do_arith(
operand : str // '+', etc
)
if g.terms[g.termx].ss == ""
// we have no term, so treat that as replacing the previously entered operation
// and if this is the very beginning and we have no prior operation, ignore it
if g.termx == 1
// starting with a plus on an empty term is ignored
return
// multiple operators in a row, rewrite the previous operator
g.terms[g.termx-1].op = operand
else
// we did have a term, advance to the next term
g.terms[g.termx].op = operand
inc g.termx
g.terms[g.termx].ss = "" // empty term| Feature | Supported | Example | Token |
|---|---|---|---|
| Semantic Indentation | ✓ | ||
| Comments | ✓ | // A comment | |
| Line Comments | ✓ | // A comment | // |