Hi Fabrice, Thanks a lot ! Indeed that does the job, which shows how wonderful Metafun is ! Best regards: Otared

On 9 Dec 2020, at 17:19, Fabrice L wrote:

Hi,

...

Le 9 déc. 2020 à 10:57, Otared Kavian a écrit :

Hi,

I have a silly question: given two points in the plane z1 = (1cm,3cm) ; z2 = (5cm, 9cm) ; the command draw z1 -- z2 withpen pencircle scaled .5pt ; draws the line segment joining z1 and z2. How could I draw the line segment which goes a little further (say 1cm) than both the end points of this segment (that is in this example, a point before z1 and a point after z2 on the straight line) . Indeed it is possible to write the equation of the line and then compute by hand the coordinates of the new end points, but I think there is a simpler way in Metafun to do this.

The shortened operation is the solution ! See MetaFun manual section 1.18

\starttext \startMPpage z1 = (1cm,3cm) ; z2 = (5cm, 9cm) ; draw (z1--z2) shortened -1cm withcolor blue ; draw (z1--z2) withcolor red ;

\stopMPpage \stoptext

Fabrice.

...

Thanks for any help: Otared

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Hi Aditya, Thanks for the alternative method, which comes handy if one wishes to extend the straight line by a different amount at either end: \starttext \startMPcode z1 = (1cm,3cm) ; z2 = (5cm, 9cm) ; z3 = 1cm * dir(angle (z2 - z1)) shifted z2 ; z4 = -.5cm*dir(angle(z2 - z1)) shifted z1 ; draw z1 -- z3 ; draw z4 -- z1 ; draw z1 -- z2 withcolor red ; \stopMPcode \stoptext Best regards: Otared

On 9 Dec 2020, at 18:37, Aditya Mahajan wrote:

On Wed, 9 Dec 2020, Otared Kavian wrote:

...

Thanks a lot ! Indeed that does the job, which shows how wonderful Metafun is !

Or, if you want to use high school algebra:

\starttext \startMPcode z1 = (1cm,3cm) ; z2 = (5cm, 9cm) ; z3 = 1cm * dir(angle (z2 - z1)) shifted z2; draw z1 -- z3 ; draw z1 -- z2 withcolor red; \stopMPcode \stoptext

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Thanks Aditya! One can learn a lot with your answers ! In the Metafun manual I see enlonged but I did not know to use it. Best regards: Otared

On 9 Dec 2020, at 21:38, Aditya Mahajan wrote:

On Wed, 9 Dec 2020, Otared Kavian wrote:

...

Hi Aditya,

Thanks for the alternative method, which comes handy if one wishes to extend the straight line by a different amount at either end:

\starttext \startMPcode z1 = (1cm,3cm) ; z2 = (5cm, 9cm) ; z3 = 1cm * dir(angle (z2 - z1)) shifted z2 ; z4 = -.5cm*dir(angle(z2 - z1)) shifted z1 ; draw z1 -- z3 ; draw z4 -- z1 ; draw z1 -- z2 withcolor red ; \stopMPcode \stoptext

Or just redefine shortened to accept a pair!

\startMPdefinitions primarydef p shortened d = reverse ( ( reverse (p enlonged -xpart paired(d)) ) enlonged -ypart paired(d) ) enddef ; \stopMPdefinitions

\starttext \startMPpage z1 = (1cm,3cm) ; z2 = (5cm, 9cm) ; draw (z1--z2) shortened (-1cm,-2cm) withcolor blue ; draw (z1--z2) withcolor red ;

\stopMPpage \stoptext

Now that if you really want to shorten a path, then cutends works better than shortened

\startMPdefinitions primarydef p shortened d = reverse ( ( reverse (p enlonged -xpart paired(d)) ) enlonged -ypart paired(d) ) enddef ; \stopMPdefinitions

\starttext \startMPpage z1 = (1cm,3cm) ; z2 = (5cm, 9cm) ; path p, q; p := z1 {up} .. {right} z2; q := p shifted (6cm, 0);

draw p withcolor red ; draw p shortened (1cm,2cm) withcolor blue ;

draw q withcolor green ; draw q cutends (1cm,2cm) withcolor blue ;

\stopMPpage \stoptext

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