Takmela: Parsing arithmetic expression example (1+2)

The first step in understanding how Takmela works! The next step is 1+2+3

// The 'arithmetic' example, with shorter names
// to make graph labels clear in visualization

e : e '+' t 
    | t ;
t : 
    NUM
    ;
    
NUM: [0-9]+;

WS skip: [ \r\n\t]*;

1+2

Trace appears confusing? This might help

Call start nonterminal
	#0: Called e/0 at the top level (will process) Processing e/0 codePos e → • e `+` t inputPos 0 Calling: e/0 with Cont e/0 ; e → e• `+` t [already processed] Processing e/0 codePos e → • t inputPos 0 Calling: t/0 with Cont e/0 ; e → t• [will process] Processing t/0 codePos t → • NUM inputPos 0 Match NUM to 1, matched; inputPos now 1 Reached end of rule, success! t/0 → 1 New continuations: e/0 → e/0 ; e → e• `+` t ; e t/0 → e/0 ; e → t• ; e
t/0 → 1, t('1')
Iteration 0
Worklist - successes jS t/0 → 1 木t('1') Worklist - continuations nJ e/0 → e/0 ; e → e• `+` t S⤚ t/0 → e/0 ; e → t•
	#1: JoinS: t/0 → 1 will resume cont: e/0 ; e → t• Processing e/0 codePos e → t• inputPos 1 Reached end of rule, success! e/0 → 1
t/0 → 1, t('1') e/0 → 1, e(t('1'))
Iteration 1
Worklist - successes jS e/0 → 1 木e(t('1')) Worklist - continuations
	#2: JoinS: e/0 → 1 will resume cont: Root/0 ; Root → e• ×Didn't reach end of input, not a successful parse
t/0 → 1, t('1') e/0 → 1, e(t('1'))
	#3: JoinS: e/0 → 1 will resume cont: e/0 ; e → e• `+` t Processing e/0 codePos e → e• `+` t inputPos 1 Match + to +, matched; inputPos now 2 Calling: t/2 with Cont e/0 ; e → e `+` t• [will process] Processing t/2 codePos t → • NUM inputPos 2 Match NUM to 2, matched; inputPos now 3 Reached end of rule, success! t/2 → 3 New continuations: t/2 → e/0 ; e → e `+` t• ; e(e(t('1')), '+')
t/0 → 1, t('1') e/0 → 1, e(t('1')) t/2 → 3, t('2')
Iteration 2
Worklist - successes jS t/2 → 3 木t('2') Worklist - continuations S⤚ t/2 → e/0 ; e → e `+` t•
	#4: JoinS: t/2 → 3 will resume cont: e/0 ; e → e `+` t• Processing e/0 codePos e → e `+` t• inputPos 3 Reached end of rule, success! e/0 → 3
t/0 → 1, t('1') e/0 → 1, e(t('1')) t/2 → 3, t('2') e/0 → 3, e(e(t('1')),'+',t('2'))
Iteration 3
Worklist - successes jS e/0 → 3 木e(e(t('1')),'+',t('2')) Worklist - continuations
	#5: JoinS: e/0 → 3 will resume cont: Root/0 ; Root → e• ✓Reached end of input, successful parse!
t/0 → 1, t('1') e/0 → 1, e(t('1')) t/2 → 3, t('2') e/0 → 3, e(e(t('1')),'+',t('2')) Root/0 → 3, Root(e(e(t('1')),'+',t('2')))✓
	#6: JoinS: e/0 → 3 will resume cont: e/0 ; e → e• `+` t Processing e/0 codePos e → e• `+` t inputPos 3 Match `+` to (eof), fail
t/0 → 1, t('1') e/0 → 1, e(t('1')) t/2 → 3, t('2') e/0 → 3, e(e(t('1')),'+',t('2')) Root/0 → 3, Root(e(e(t('1')),'+',t('2')))✓
Iteration 4
Worklist - successes nJ Root/0 → 3 木Root(e(e(t('1')),'+',t('2'))) Worklist - continuations
(No new calls or successes that can be further processed)
Iteration 5 [Fixed point reached]