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253 changes: 109 additions & 144 deletions easylang.md
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filename: easylang.el
---

**Easylang** is a simple programming language with built-in graphical functions and an easy-to-use and offline usable browser IDE. Its simple syntax and semantics make it well suited as a teaching and learning programming language. You can also use it to write graphical applications that you can embed in a web page.

*Easylang* is statically typed and has as data types only strings and numbers (floating point), resizeable arrays of strings and numbers and arrays of arrays.
**Easylang** is a simple programming language with built-in graphical functions and an easy-to-use and browser IDE. Its simplified syntax and semantics make it well suited as a teaching and learning programming language. You can also use it to write graphical applications that you can embed in a web page.

[The browser IDE](https://easylang.online/ide/) includes various tutorials, including one for beginners.

```
print "Hello world"
#
# number variable (64 bit floating point)
#
h = 3.14
print h
print "Hello Easylang"
#
# string variable
f = 2 * pi
print "Numbers are floating point: " & f
print "and are implicitly converted to strings"
#
str$ = "monkey"
# strings can grow
str$ &= " circus"
str$ = "Strings can"
str$ &= " grow"
print str$
#
# blocks end with 'end' or a dot, a newline has no
# other meaning than a space
# Blocks end with 'end' or a dot, newline is just a token seperator
#
for i = 1 to 5
sum += i * i
for i = 1 to 3
print i * i
.
print sum
#
# functions have value and reference
# parameters, no return values
#
func gcd a b . res .
# a and b are value parameters
# res is a reference parameter
while b <> 0
# h is a local variable, because
# it is first used in the function
h = b
b = a mod b
a = h
.
res = a
func gcd a b .
# a and b are value parameters
while b <> 0
# h is local, since it is first used in the function
h = b
b = a mod b
a = h
.
return a
.
call gcd 120 35 r
print r
#
# strings can be concatenated and numbers are
# automatically converted to strings
#
print "1 + 2 = " & 1 + 2
print "The greatest common divisor of 182 and 28: " & gcd 182 28
#
# array of numbers
func gcdr a b .
if b = 0 : return a
return gcdr b (a mod b)
.
print "Recursively calculated: " & gcd 182 28
#
a[] = [ 2.1 3.14 3 ]
# Arrays are 1-based and can grow
#
# arrays can grow
a[] = [ 13 3.14 3 ]
a[] &= 4
print a[]
for i = 1 to len a[] : write a[i] & " "
print ""
#
proc sort &data[] .
# data is a reference parameter
for i = 1 to len data[] - 1
for j = i + 1 to len data[]
if data[j] < data[i] : swap data[j] data[i]
.
.
.
sort a[]
print "Sorted: " & a[]
#
# arrays, strings and numbers are copied by value
#
b[] = a[]
a[] &= 4
print a[] ; print b[]
a[1] = 111
a[4] = 777
print "a[]:" & a[] & " b[]:" & b[]
#
# array swapping ist fast
#
swap a[] b[]
print a[] ; print b[]
#
# array of strings
#
fruits$[] = [ "apple" "banana" "orange" ]
print "a[]:" & a[] & " b[]:" & b[]
#
# for-in iterates over the elements of an array
#
for fruit$ in fruits$[]
print fruit$
.
fruits$[] = [ "apple" "banana" "orange" ]
for fruit$ in fruits$[] : print fruit$
#
# strings are also used for single characters
#
letters$[] = str_chars "ping"
letters$[] = strchars "ping"
print letters$[]
letters$[1] = "o"
print str_join letters$[]
letters$[2] = "o"
print strjoin letters$[] ""
#
# 2-dimensional arrays are arrays of arrays
# this defines 3 arrays with length 4
# a 2-dimensional array is an array of arrays
#
len a[][] 3
for i range len a[][]
len a[i][] 4
for i = 1 to len a[][]
len a[i][] 3
a[i][i] = 1
.
a[1][2] = 99
print a[][]
#
# builtin functions
# some builtin functions
#
if sin 90 = 1
print "angles are in degree"
print "Angles are in degree"
.
print pow 2 8
# seconds since 1970
print floor sys_time
# random numbers
print randomf
print random 6 + 1
#
# hour and minutes
print substr time_str sys_time 11 5
#
print str_ord "A"
print str_chr 65
#
# set number format
print "A kibibyte: " & pow 2 10
print "Seconds since 1970: " & floor systime
print "Random between 0 and 1: " & randomf
print "A dice roll: " & random 6
print "Current time: " & substr timestr systime 12 5
print strcode "A" & " is " & strchar 65
#
# set number output format
#
numfmt 0 4
print sqrt 2
print pi
print logn 10
#
a$[] = str_split "10,15,22" ","
print "Square root of 2: " & sqrt 2
print "Pi: " & pi
print "10's logarithm of 999: " & log10 999
#
a$[] = strsplit "10,15,22" ","
print a$[]
print 2 * number a$[0]
print 2 * number a$[1]
print len a$[]
print len "Hello"
#
# With 'break n' you can leave nested loops and a function
#
names$[] = [ ]
func name2id name$ . id .
for id range len names$[]
if names$[id] = name$
# leave loop and function
break 2
.
.
names$[] &= name$
.
call name2id "alice" id ; print id
call name2id "bob" id ; print id
call name2id "alice" id ; print i
print len a$[1]
#
# with 'repeat' you can make loops, which you can leave
# in the loop body using 'until'
# "input" reads a string from the "input_data" section, if it exists,
# otherwise via a prompt.
#
sum = 0
repeat
s$ = input
until s$ = ""
sum += number s$
s$ = input
until s$ = ""
sum += number s$
.
print "sum: " & sum
#
# "input" reads a string from the "input_data" section,
# if it exists, otherwise via a prompt.
print "Sum of input data: " & sum
#
input_data
10
-2
6
567
1023
69
```

Built-in graphic primitives and event-driven programming

```
# simple drawing with the mouse
#
set_linewidth 4
set_color 900
# the colors are coded from 0 to 999, with
# the left digit specifying the red component,
# the middle digit the green component and
# the right digit the blue component.
#
#
glinewidth 4
gcolor 900
# the colors are coded from 0 to 999, where the
# decimal digits specify the RGB components
#
on mouse_down
down = 1
move_pen mouse_x mouse_y
# moves the drawing pen to the actual mouse position
draw_circle 2
down = 1
mx = mouse_x
my = mouse_y
gcircle mx my 2
.
on mouse_up
down = 0
down = 0
.
on mouse_move
if down = 1
draw_line mouse_x mouse_y
.
if down = 1
gline mx my mouse_x mouse_y
mx = mouse_x
my = mouse_y
.
.
```

```
# an animated pendulum
#
ang = 45
on animate
# The animate event occurs after each screen refresh.
#
clear_screen
move_pen 50 50
draw_circle 1
x = 50 + 40 * sin ang
y = 50 - 40 * cos ang
draw_line x y
draw_circle 5
vel += sin ang / 5
ang += vel
# The animate event occurs after each screen refresh.
gclear
gcircle 50 50 1
x = 50 + 40 * sin ang
y = 50 + 40 * cos ang
gline 50 50 x y
gcircle x y 6
vel += sin ang / 5
ang += vel
.
ang = 10
```

* [More about Easylang](https://easylang.online/)
* [More about Easylang](https://easylang.online/apps/)

* [Source code](https://github.com/chkas/easylang)
* [Source code](https://github.com/chkas/easylang/)