# Changes between Initial Version and Version 3 of Ticket #28554

Ignore:
Timestamp:
10/04/19 18:43:36 (2 years ago)
Comment:

New commits:

 ​0c645ca 'set_restriction' added + 'display' modified + naming modified

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• ## Ticket #28554

• Property Commit changed from to 0c645ca987eb13c63cfc7841aac1c4d320eec253
• Property Branch changed from to u/gh-DeRhamSource/scalar_field_restrictions
• ## Ticket #28554 – Description

 initial This solution is quite unhandy and becomes even more so for more complicated scalar fields. In this ticket, I try to solve this issue by adding a set_restriction method (similar to tensor fields) and modifying the display method. How is a scalar field implemented which is split into different expressions in one particular chart? Take for instance a scalar field f on the real line with standard "top" chart x, defined via f(x)=0 for x<-1, f(x)=x+1 for -1<=x<0, f(x)=1-x for 0<=x<1 and f(x)=0 for x>=1. Currently, this is solved by using {{{ f = M.scalar_field( unit_step(x + 1)*unit_step(1 - x)*(1 - abs(x)) ) }}} (see https://trac.sagemath.org/ticket/28519#comment:46). This solution is quite unhandy and becomes even more so for more complicated scalar fields. **This ticket includes:** - modification of namings after algebraic operations, such as f*g (f \cdot g for LaTeX code), f/g and f+g - display method modified in such a way that all distinct expressions are shown (a small slowdown in computation time) - set_restriction method added smilar to tensor fields - _is_zero attribute copied for a copy