Autolisp if - Cond

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if - This function evaluates an expression to decide which expressions to do afterwards.

U T L

thisIsTrue thenDoThis)

Syntax : (if

thisIsTrue thenDoThis

Syntax : (if

thisIsTrue

Syntax : (if

thisIsTrue thenDoThis

thenDoAllOfThis - Any valid autolisp expressions. elseDoAllOfThis - Any valid autolisp expressions. progn - Simply means there will be more than one statement here.

 A 

(if T (princ 3)) (if T (princ 3)(princ 4))

D

evaluates to True

 V 

evaluates to False

 A 

T

D

(progn (progn elseDoAllOfThis) elseDoAllOfThis) )

elseDoThis - Any valid autolisp expression.

P

E

(progn (progn thenDoAllOfThis) thenDoAllOfThis) elseDoThis)

thenDoThis - Any valid autolisp expression.

S

C

elseDoThis)

thisIsTrue - Any valid autolisp expression that evaluates to true or non nil.

I

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Syntax : (if

Syntax : (if thisI sTrue ( progn progn then DoAllOfThis) ( progn progn elseDoAllOfThis) elseDoAllOfThis) )

O

N

cond

(if nil (princ 3)(princ 4))

returns 3 returns 3 because T always

returns 4 because nil always

(if (= nil T) (princ 3)(princ 4)) returns 4 because nil does not equal

(if (= 3 3) (princ 3) (princ 4))

returns 3

(if (= 3 4) (princ 3) (princ 4))

returns 4

-------------------------------------------------------------------------------------------------(if (= 3 3) (progn (princ 3)

returns 3

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(princ 5) )

T )

U T

--------------------------------------------------------------------------------------------------(if (= 3 3) (progn

O R 

L

returns 5

(princ 5) )

I  A 

returns 3

(princ 3)

(progn

program never gets inside

(princ 8)

here because 3 = 3 program never gets inside here

(princ 9)

because 3 = 3 )

 A  U

)

-------------------------------------------------------------------------------------------------(if (= 3 4)

T O L

(progn (princ 3)

program never gets inside here because 3 does

(princ 5)

program never gets inside here because 3 does

not equal 4

not equal 4

I

) (progn

S

prints 8

(princ 8)

P

prints 9

(princ 9) )

 A 

)

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cond - This function test conditions until one of them is true. At that point it exits the function. Syntax : (cond (ifThisIsTrue

thenDoThis)

(elseIfThisIsTrue

thenDoThis)

(elseIfThisIsTrue

thenDoThis)

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C

Syntax : (cond

E

(ifth isIs True

(progn then DoAllOfThis) )

(elseIfThisIsTrue

D T U

thenDoThis)

(elseIfthisI sTrue

(progn thenDoAllOfThis) )

(elseIfthisIsTrue

thenDoThis))

(elseIfthisI sTrue

(progn thenDoAllOfThis) )

(elseIfthisIsTrue

thenDoThis))

)

T

thisIsTrue - Any valid autolisp expression that evaluates to true or non nil. thenDoThis - Any valid autolisp expression.

O

elseDoThis - Any valid autolisp expression.

R 

thenDoAllOfThis - Any valid autolisp expressions. elseDoAllOfThis - Any valid autolisp expressions.

I

progn - Simply means there will be more than one statement here.

 A  (cond

L

( (= 1 1) (princ "True") ) ( (= 1 2) (princ "True") )

 A  U

returns True

-------------------------------------------------------------------------------------------------(cond

T

( (= 1 0) (princ "True") )

skips because 1 does not

equal 0

L I

doesn't make it to this

point )

O

prints TRUE and exits

( (= 1 1) (princ "True") )

prints TRUE and exits

( (= 1 2) (princ "True") )

doesn't make it to this

point returns True

)

S --------------------------------------------------------------------------------------------------

P

(cond ( (= 4 3) (princ "True") )

 A  D

skips because 4 does not

equal 3 ( (= 4 2) (princ "True") )

skips because 4 does not

( (= 4 1) (princ "True") )

skips because 4 does not

equal 2

equal 1

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)

-------------------------------------------------------------------------------------------------(cond ( (= 4 3) (princ "True") )

skips because 4 does not

equal 3

 V   A 

( (= 4 2) (princ "True") )

skips because 4 does not

( (= 4 1) (princ "True") )

skips because 4 does not

equal 2

equal 1

N

prints "Nothing" because

( T (princ "Nothing") )

T = True

C

returns "Nothing"

)

--------------------------------------------------------------------------------------------------

E

set a variable

(setq a

D

(cond ( (= 4 3) (princ "True") )

T U T O R  I  A  L

skips because 4 does not

equal 3 ( (= 4 2) (princ "True") )

skips because 4 does not

( (= 4 1) (princ "True") )

skips because 4 does not

equal 2

equal 1 prints "Nothing"

( T (princ "Nothing") )

because T = True returns "Nothing"

)

sets variable [a] to

)

"Nothing" End of Conditional Statement s

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