HP 3000 Manuals HP 3000 Manuals
FOR Statement
Table 6-7. FOR Statement
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| SPL | HP C/XL Equivalent |
| | |
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| | |
| for-statement: | for-statement: |
| | |
| 1. FOR test-var := init-val | 1. for ( test-var = init-val ; |
| UNTIL end-val | test-var <= end-val ; |
| DO loop-statement | test-var++ ) |
| | loop-statement |
| | |
| 2. FOR test-var := init-val | 2a. for ( test-var = init-val ; |
| STEP step-val | test-var <= end-val ; |
| UNTIL end-val | test-var += step-val ) |
| DO loop-statement | loop-statement |
| | |
| | 2b. for ( test-var = init-val ; |
| | test-var >= end-val ; |
| | test-var += step-val ) |
| | loop-statement |
| | |
| 3. FOR * test-var := init-val | 3. for ( flag = 1 , test-var = init-val ; |
| UNTIL end-val | flag || test-var <= end-val ; |
| DO loop-statement | flag = 0 , test-var++ ) |
| | loop-statement |
| | |
| 4. FOR * test-var := init-val | 4a. for ( flag = 1 , test-var = init-val ; |
| STEP step-val | flag || test-var <= end-val ; |
| UNTIL end-val | flag = 0 , test-var += step-val ) |
| DO loop-statement | loop-statement |
| | |
| | 4b. for ( flag = 1 , test-var = init-val ; |
| | flag || test-var >= end-val ; |
| | flag = 0 , test-var += step-val ) |
| | loop-statement |
| | |
| | |
| | The generic syntax is: |
| | |
| | for ( init-expr ; |
| | test-expr ; |
| | incr-expr ) |
| | statement |
| | |
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| Continued |
| |
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FOR Statement(cont.)
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| SPL | HP C/XL Equivalent |
| | |
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| | |
| init-val, step-val, and end-val are | In general, the HP C/XL expressions are |
| evaluated and stored. test-val is set to | independent, and may even be omitted! The |
| init-val. | values in the expressions may be changed in |
| | the body of the for statement. |
| test-val is compared to end-val. If | |
| step-val is positive or omitted, and | The first expression (e.g., init-expr) is |
| test-val is less than or equal to end-val, | evaluated only once, on initial entry into |
| loop-statement is executed. If step-val is | the for statement. |
| negative, and test-val is greater than or | |
| equal to end-val, loop-statement is | For each iteration, the second expression |
| executed. If the test fails, the for | (e.g., test-expr) is evaluated. If it is |
| statement terminates. | false, the for statement is terminated. If |
| | it is true, the loop-statement is executed, |
| After loop-statement is executed, test-val | the third expression (e.g., incr-expr) is |
| is incremented by step-val or 1, and it is | evaluated, and the for statement iterates. |
| compared with end-val as above. | |
| | |
| | In the simplest case, init-expr initializes |
| | a test-var, test-expr tests it, and |
| | incr-expr increments it. |
| | |
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| | |
| | Formats 2a and 4a deal with the case where |
| | step-val is positive. Formats 2b and 4b |
| | handle the case where step-val is negative. |
| | There is no easy way to combine the |
| | formats. |
| | |
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In HP C/XL, the three expressions can actually contain multiple
expressions, separated by commas. The last or right-most becomes the
value of the expression. This is the method used to solve the SPL "*"
alternative, in formats 3 and 4. An arbitrary variable, flag is set to
1. Since flag is true on the first pass, it forces the execution of
loop-statement. On subsequent passes, it is 0 or false, so the normal
end testing takes over.
Table 6-8. FOR Statement Examples
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| SPL | HP C/XL Equivalent |
| | |
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| FOR I:=ABC STEP 1 UNTIL 99 | for ( I = ABC ; I <= 99 ; I++ ) |
| DO A(I):=B(I)-X; | A[I] = B[I]-X; |
| | |
| | |
| FOR * I:=ABC STEP -1 UNTIL 0 | for ( ONCE = 1 , I = ABC ; |
| DO A(I):=B(I)-X; | ONCE || I >= 0 ; |
| | ONCE=0 , I-- ) |
| | A[I] = B[I]-X; |
| | |
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The SPL FOR * construct may also be easily emulated by an HP C/XL
do-while statement, as illustrated by the following statements:
I = ABC ;
do A[I] = B[I]-X ; while (--I >= 0);