Language Cheatsheet

This is a work in progress.

Atoms

• nil
• booleans: true or false
• numbers: 0 1 2.3 4.5e6 0b111011 0777 0x123 123_456_789
• strings: "Hello world"

Expression shortlist

• generic values: a, b, c...
• generic symbols: $a, $b, $c

a + b is an expression a + b ; c + d is an expression sequence (also an expression) ; and a newline (also a comma in many contexts) are expression separators

Expression separators are optional, where the expressions are unambiguous. So, a+b; c+d , a+b c+d and

a+b
c+d

are equivalent (they are all an expression list).

Examples

Symbol definition

a = 100 \\ grammar sugar :let(a, 100) \\ Internal form The symbol a gets defined in the current evaluation context

Control flow

if expr exprIfTrue   //grammar sugar
else exprIfFalse

:if(&expr  &exprIfTrue &exprIfFalse={}) // internal representation

The & marks an eta-parameter which is passed as-is, without eager-evaluation.

Take the following example:

a = someFunc()
if a > 100 {
   print("A is greater than 100:" a)
   a = 0 }
else print("A is not big enough")

The {...} is actually an expression sequence, itself an expression, which is evaluated according with the control flow. This program is equivalent to:

a = someFunc()
:if( a > 100 { print("A is greater than 100:" a) a = 0 } print("A is not big enough"))

or (separators added for readability):

a = someFunc()
:if( a > 100,
   { print("A is greater than 100:" a), a = 0 }, 
   print("A is not big enough")
)

And this is equivalent to:

:let(a, someFunc())
:let(ifTrue, {{print("A is greater than 100:", a=0}})
:let(ifFalse, {{print("A is greater than 100:" a)}} )
:if( a > 100 ifTrue ifFalse)

The second parameter of let is evaluated eagerly, which "strips" the first pair of {}, as {expr} evals to expr.

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