French President Valery Giscard d'Estaing and Socialist leader Francois Mitterand took a long stride yesterday toward erasing the bitter left-right divisions that have long made it impossible to talk of a "loyal opposition" in France.

Mitterand called on Giscard for an hour and forty minutes to discuss the president's appeal last week for a reasonable cohabitation" between the government and the opposition.

Mitterand said that he had wanted for some time to discuss "the grand interests of France and the French people" with the chief of state. It was Mitterand's first call upon an elected French president.

"It is in the higher interest of the country that beyond our disagreements . . . there should be new rules and new customs in what might be called the daily practice democracy," Mitterrand said.

"Of course," he cautioned, "it is not a question of reversing our roles. It is for the majority to govern. It is for the opposition to exercise its rights to criticize and to propose. But it is for both to respect what they represent together . . . the national community."

It has long been Giscard's stated dream to end the polarization of French politics. Top members of Giscard's entourage say that one of the late President Charles de Gaulle's "historic errors" was to accentuate the polarization to guarantee that the French right would always remain in power against a Communist-dominated left.

This policy was summed up in Gaullist philsopher Andre Malraux's often-quoted statement that "between the Communists and us there is nothing."

Since both Giscard and Mitterand stand between the Communists and the Gaullists, they aand the forces they represent have an interest in denying the two extremes a monopoly on French political life.

Communist leader Georges Marchais also has accepted a presidential invitation to call at the Elysee and is to confer with Giscard later this week.

Giscard publicly invited all the major political, labor union, professional and business organization leaders to discuss with him the political and economic priorities that his new Cabinet should pursue. Mitterrand said last night that Giscard followed it up with a personal invitation.

Gaullist Party leader Jacques Chirac, Giscard D.'Estaing's unannounced rival for leadership of the government majority also called on Giscard and and made a brief statement amounting to a "no comment" after a one-hour visit yesterday morning.

Chirac's reticence contrasted with Mitterrand's long declaration. It was also widely noted that the opposition leader spent nearly twice as much time with the president as Chirac.

Both Mitterrand and Elysee spokesman Pierre Hunt stressed that there was no question of either side modifying its basic positions, but that it is desirable for opposing political forces in France to learn to live together.

The recently concluded legislative elections underlined that there are four main forces in France rather than two de Gaulle insisted. Giscard's own centrist allies won almost as many votes and National Assembly seats as the Gaullists, who had previously dominated the right. The Socialists out-polled the Communists for the first time since World War II.

In addition to Marchais the Communist leader of the General Labor Confederation, Georges Seguy, also accepted Giscard's invitation. For the Communists, being received at the Elysee gives them an added measure of respectability.

Chirac resigned as Giscard's prime minister in 1976 because the president refused his advice that the only way to remain in power against the left was to conduct a traditional red scare campaign.

Throughout the recent campaign, the leftist opposition kept stressing that for French democracy to be healthy it must be possible for the left and the right to succeed each other.

Goernment backers asserted that the kid of natural succession that takes place in countries like Britain, West Germany and the United States is simply not possible where the Communist Party is so powerful.

With many Socialists now convinced that it is indeed not possible that the Communists would permit the left to acheive power unless the Communist Party dominates it, Giscard's invitation appealed to Socialist thinking that their party must now work to become so dominant on the left that the Communist can neither veto a leftish victory nor serve as the right's permanent excuse for barring leftish rule.

Mitterand said that it would be a disservice to the country for there to be any confusion between the leftish and the rightish views of French society. "By preserving the possibilities of succession," he said, "we will preserve the possibilities of democracy."

He said he and Giscard had not discussed the government's program. He offered a long list of socialist criticisms of past government treatment of the opposition, including recent accusations of voting frauds involving the proxies of French citizens living abroad.

If Giscard's "happy initiative" is to bear fruit, Mitterrand said, such practices should be abolished. The Elysee spokesman called the meeting "sober and relaxed" and said that Giscard desires more such meetings when events justify them.