61 lines
3.0 KiB
Markdown
61 lines
3.0 KiB
Markdown
## Program Control
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### Statement block
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A statement block binds single statements enclosed in a curled paranthesis pair.
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```
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{ Φ Φ Φ .. }
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```
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### Conditional Branches
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There is only a `if then else` statement branching to conditional statements. Conditional statements can be replaced by statement blocks, too.
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| Statement | Description |
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|:--|:--|
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| `if ε:Φ:Φ:.. ` | If expression ε is true (not equal 0), then the following line statements are executed. |
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| `if ε then Φ:Φ:.. ` | If expression ε is true (not equal 0), then the following line statements are executed. |
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| `if ε { Φ }` | If expression ε is true (not equal 0), then the following block statement is executed. |
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| `if ε then { Φ }` | If expression ε is true (not equal 0), then the following block statement is executed. |
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| `if ε Φ1 else Φ2` | If expression ε is true (not equal 0), then the following statement Φ1 is executed else Φ2. |
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| `if ε { Φ1 } else { Φ1 }` | If expression ε is true (not equal 0), then the following block statement Φ1 is executed, else Φ2. |
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### Loops
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There are conuting, conditional, and unconditional loops. Body statements can be replaced by statement blocks, too.
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| Statement | Description | F-Stack Frame |
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|:--|:--|
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| `for i = a,b: Φ: Φ: ..` | Counting loop starting with *i*=*a* and terminating with i=b. The default increment value is one. | F(b,control address,end address,'F') |
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| `for i = a,b do Φ: Φ: ..` | Counting loop starting with *i*=*a* and terminating with i=b. The default increment value is one. | F(b,control address,end address,'F') |
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| `for i = a,b,s: Φ: Φ: ..` | Counting loop starting with *i*=*a* and looping as long as *i*<=*b*. The increment value (step size) is *s*. | F(b,step,control address,end address,'F') |
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| `while ε: Φ: Φ: ..` | Conditional loop checking the expression ε at start. | F(start address,end address, 'W') |
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| `while ε do Φ: Φ: ..` | Conditional loop checking the expression ε at start. | F(start address,end address, 'W') |
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| `do Φ: Φ: .. while ε` | Conditional loop checking the expression ε at end. | F(start address,end address, 'D') |
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| `repeat Φ` | Endless (service) loop, but breakable. | F(start address,end address, 'D') |
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| `break` | Leave current (innerst) loop | - |
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| `continue` | Branch to end of loop body (starting new loop iteration) | - |
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### Functions and Procedures
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| Statement | Description | F-Stack Frame |
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|:--|:--|
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| `proc pname { Φ } ` | Defines a procedure (no arguments, no return value) | - |
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| `func fname(a,b,c) { Φ } ` | Defines a function with arguments (a,b,c) and a return value. | - |
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| `return` | Return from procedure call (no return value) | - |
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| `return ε` | Return from function call with return value ε | - |
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| `call pname` | Call procedure | F() |
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| `call fname(ε,..)` | Call function without return value | F() |
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| `x=call fname(ε,..)` | Call function (in expression) with return value | F() |
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### Program Flow Control
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| Statement | Description | F-Stack Frame |
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|:--|:--|
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| `go` | Resume program | - |
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| `stop` | Suspend program | - |
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